Process for preparing alkane sulfonic acids



Patented Apr. 3, 1951' UNITED STATES PATENT OFFICE PROCESS FOR PREPARINGALKANE SULFONIC ACIDS John K. Fincke, Dayton, Ohio, assignor to MonsantoChemical Company, St. Louis, Mo., a corporation of Delaware No Drawing.Application February 24, 1948,

Serial No. 10,588

Claims. (Cl. 260513) be that described by McBain and Williams (JACS 55,2250 (1933) This method involved the preparation of the lead mercaptideby the action of hot alcoholic lead acetate upon the alkyl mercaptan,the oxidation of the lead mercaptide by means of 50% nitric acid,followed by the conversion of the lead alkyl sulfonate to alkylsulfonates by refluxing in isopropyl alcohol to which dry hydrogenchloride is added. More recently it has been proposed to prepare a kanesulfonic acids by the direct oxidation of the mercaptan to the sulfonicacid by means of nitric acid. This method, however, in general yields aproduct which is somewhat colored and of a low degree of purity.

It has also recently been proposed to oxidize dialkyl sulfides by meansof nitrogen oxides. This method, however, is not applicable to ,B-(alkylmercapto) ethanols having more than 8 carbon atoms in the alkyl group.

I have now discovered that B-(alkyl mercapto) ethanols may be directlyoxidized to the valkyl sulfonic acid by treatment with concentratednitric acid and a pure form of the alkane sulfonic acid obtained. Forthe present process the alkyl group should contain at least 8 carbonatoms and may contain up to and including 18 carbon atoms. The processis best carried out by employing an excess of nitric. acid overthatshown by the reaction as written below. A suitable temperature is thattemperature at which evolution of brown fumes of nitrogen peroxide isobserved. Exploratory tests have shown that the reaction may beconducted at any temperature up to 100 C. In general the besttemperatures range from 40 C. to 80 C.

The reaction apparently follows the course indicated bythe equation:

where R'is alkyl and preferably has from 8 to 18 carbon atoms. Theproduct produced by the present process is of a high degree of purity,that is the purity approximates The fi-(alkyl mercapto) ethanols may beprepared by the addition of one mole of ethylene oxide to the alkylmercaptan. The-mercaptan employed may be either a primary ora secondarymercaptan.

The following examples illustrate, but do not limit, the inventionherein described and claimed:

Example 1 Forty grams of fi- (n-octyl mercapto) ethanol was addeddropwise to 1'70 cc. of concentrated nitric acid contained in a 500 cc.flask. After the addition was complete, the flask contents were warmedto 80 for approximately one-half hour. The excess nitric acid wasremoved under a vacuum. When almost all of the free nitric acid had beenremoved, a very vigorous reaction took place, oxides of nitrogen beinggiven 01f and the mass becomingquite hot. After completion of thereaction the reaction mass was dissolved in ethyl alcohol, neutralizedwith caustic soda and fllteredhot. The alcohol insoluble material wasdiscarded. The alcoholic solution was then boiled down, crystallized and23.5 grams of crystals obtained.

-A small portion of the product was acidified with HCl. The NaClformedwas removed and neutra ized withphenyl hydrazine in alcohol andprecipitated from cold ether. The product was recrystallized from etherand melted at 87-89 C. In agreement with that found by Latimer and Bost,JACS 59, 2500 (1 937) the product is n-octane sulfonic acid.

Example 2 Fifty-five grams of fi-(n-dodecyl mercapto) ethanol was addeddropwise to cc. of concentrated (1.42 S. G.) HNO3 with stirring, thetemperature being kept below 45 C. Vigorous evolution of oxides ofnitrogen took place, which continued for approximately three hours. Atthe end of this time the flask was warmed to 50 C. to 60 C. One. waterbath, the solution becoming clear and wine-red in color. The flaskcontents were then poured into a'2-liter beaker and diluted toapproximately 1500 cc. with water. The product was neutralized to a pHof 8 with 40% caustic soda and then cooled in an ice bath. Very flnecrystals appeared, which were removed by filtration. The productsoftens'at C. and melts,

above 235 C. The product is l-dodecane sulfonic acid. This was confirmedby preparing the henzyl aniline salt which melts at 89.5-90.5 C.According to Noller et a1., JACS 55, 1090 (1933), the benzyl anilinesalt of l-dodecane sulfonic acid melts at 90-90.2 C.

1 t EgJample} t 280 cc. of concentrated nitric acid was charged to a1-liter, 3-necked flask fitted with mechanical stirring, droppingfunnel, thermometer and a reflux condenser. The acid w-as warmed -to- 80C. and then 53.0 grams of n-dodecyl mercapto ethanol was added slowlydropwise. The temperature was maintained at 80 Q;-by-the;-heat of thereaction. The reactionproduct'foamed quite vigorously toward the end ofthe addition. The flask and contents were rnaintained at 80 C. until allevolution of the oxides of nitrogen;

had ceased. The contents were then,a lowed to stand overnight,then,warmed to 60C; in the morning and diluted with 500 cc. of distiledwa- *ter: The product was neutralized with40% caustic soda, allowedtO-stand overnight. thencooled inan-ice bath and crystals filtered oiT.The crys- 25 -ta-ls were-washed with ice waterand were dried. -"'Yied;63.2 grams of dodecane sodium sulfonate corresponding to 62.0% yield.

Example 4 ne gram moleof fi-(n-octadecyl mercanto) ethanol is treatedwith 'l gram moles of HNO3 as 1.30 specific gravity nitric acid withstirring,

;'.;.the:.; temperature being maintained during the waddition- -below,-50"- Afteralbot the nitric :.;-acid;has been added the -reaction -massis refluxed dissolvethe; sulfonic -acid; and the sulfonic acidneutralized ith caustic-soda; The-neutralized s olutien-is filtered.-The alcoholic neutral solurtion; is t en boiled down in order-to.-cr-ystallize the product whicl'ris =-recovered as pure, white--crystals--of octadecanesodium 'sulfonate.1-The -,-sulfonicacid-;isobtained bv=-acidification of the alcoholic solution;- with :HCl;--filtration of-: 1 the solution to remove NaCl and evanoration of thealcohol to crystallize thesulfonic acid.

Example 5 H 1 100,. grams of .e.--(n-decyl.mercaptola-et anol was lacedin a2-liter, "3-necked flask, 250 cc.

' of1distilled-water. .was BdClGflgfOljlfiWQd-bV 14000. C 01concentrated (1.42 S G.)-. HNO; added and ":.bh87,fia Skstirred '{fOItwo hours.- Considerable heat-of ,reactionwasevolved.- Aft rthe flaskshad cooled down somewhatdt was warmed by-the application of heat to atemperature-of 90 C. to 100 C. One gram of ammonium vanadate was thenadded and reflux-ing was continued for an additional, hour, The productwas, recovered by solution in alcohol, neutralization and crys-'tallization .of the; sodiumsalt of decane s ulfonic acid. -The.free, sulfonic acid was obtained by acidification with alcohol, followed byfiltration and crystallization.

- firmin 6 105-grams of B-(n-do'decvl mercapto)- ethanol was added dopwise'to 1' cc. of concentrated (specific-gravity 1.4) HNOa in a-4-literbeaker. 'The temperature was maintained at 50 C. to

-' 60" C.- during addition. After about six hours "the material wasveryvis'cous and almost cornpletely water-soluble. An additional 180 cc;of

nitric-acid was added to insure completion of the reaction.

500 cc. of water was added, the product neutralized with 40% sodiumhydroxide and the crystals filtered ofi and dried. 81.5 grams wereobtained corresponding to a 70% yield of dodecane sulfonic acid.

It is possible to obtain the desired reaction by the employment of amore dilute nitric acid j than ;the., 1.42 3 G. HNQ; employed in some ofthe examples. However, when'this is done the 10 time of reaction issomewhat increased, and it -will be desirable in this case to increasethe tem- .--perature. .by..the application of external heat to thereaction container.

The alkane sulfonic acids produced by the present process may be used assurface-active 1 agents, particularly for detergents, wetting agents andsurface-tension modifiers.

What I .claimis:

r --1 .-The process for producing alkane sulfonic acids which comprisestreating B-(alkyl mercap to) ethanol with nitric acid at a temperatureat which nitrogen peroxide is evolved and the C2H4OH group presenttherein is oxidizedand recovering alkane sulfonic acids from thereaction product.

' ,2. The process for producing alkane sul'fonic acids which comprisestreatingB-(alkyl mercapto) ethanol with at least 6 'moles of nitric acidat a temperature at which nitrogen peroxide is evolved and the C2H 4OHgroup present therein is oxidized and thereupon recovering alkanesulfonic acids from the reaction product. 3. process forproducing-alkane sulfonic acids which comprises treating li-(allgyl 'mercapto )ethanol, wherein the alkyl "group containslfrom- 8 to 18carbon'atoms with at least rnQles of'I-INOB per'mole or e-(alk'ylmercapto) ethanols, at a temperature at which nitrogen peroxide isevolved and the C'2H4OH group present herein is oxidized and thereuponrecovering alkane sulfonic' acid from the reaction .product.

4. The process for producing alkane su lifonic acids which comprisestreating p- (alkyl mercapto) ethanol, wherein the alkyl Lgroupfcontainsfrom 8 to 18 carbon atoms with at least 6 -mo1es of HNOg per mole ofe-(alkyl mercapto) V ethanol at a temperature below 100 0., whereby "theC2H4OI-I group present therein is oxidized. The process or producingalkane'sulfonic acids which comprises treating fi-(alkyl mercapto)ethanol, wherein the alkyl group contains from 8 to 18 carbon atoms withat least 6 moles of, HNO per mole of e-(alkyl mercapto) ethanol ata'temperature between 40? C and 80f 0., whereby the 'C2H4OI-I grouppresent therein is oxidized. v 7

J OI-IN KQ FINCKE.

6 v REFERENCES CITED I The following references are of record in thefile of this patent:

'UN'ITEDSTATES PATENTS Num er Name Date 1,925,191 Keller Sept. 5,19331,966,187 Schirm July 10, 1934 2,204,210 Farlow June 11, 1940 2,338,830Werntz Jan. 11, 1944 2,346,102 De Simo Apr. 4, 1944 2,374,983 De SimoMay 1, 1945 OTHER REFERENCES

1. THE PROCESS FOR PRODUCING ALKANE SULFONIC ACIDS WHICH COMPRISESTREATING B-(ALKYL MERCAPTO) ETHANOL WITH NITRIC ACID AT A TEMPERATURE ATWHICH NITROGEN PEROXIDE IS EVOLVED AND THE -C2H4OH GROUP PRESENT THEREINIS OXIDIZED AND RECOVERING ALKANE SULFONIC ACIDS FROM THE REACTIONPRODUCT.